Not sure about partial mashes. But if doing a beer with pilsner malt as the base malt, boil for 90 minutes. Pilsner malt has higher levels of SMM which causes DMS. Because of the higher levels of SMM in pilsner malt compared to 2row, it's advised to boil 90 minutes. DMS is volitle and driven off during the boil.

With that being said, assuming that you are brewing 5 gallons, 3 lbs of pilsner is a percentage of the fermentables, especially a higher gravity brew like a triple. So 60 minutes you maybe fine.